<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button>click</button>
    <script>
        let button = document.querySelector('button');
        const handleClick = ()=>console.log('clicked');
        //button=EventTarget 监听在button上发生的click事件，当发生的时候执行handleClick
        button.addEventListener('click',handleClick);


    </script>
</body>
</html>